The present invention relates to a gasket in general and, in particular, to a cylinder head gasket and a method of manufacturing such a gasket.
In a known method of manufacture of cylinder head gaskets, sheets of soft material such as asbestos fibers are combined with synthetic rubber and rolled on both sides of a metal carrier sheet. The sheets of soft material are impregnated with polymer impregnating means for improvement of their durability with respect to cooling and lubricating and, also, to provide a seal along the edges of the gasket after openings to the combustion chamber have been formed and provided with metallic rim borders. Furthermore, the surfaces of the cylinder head gasket are provided with a coating layer so as to improve the microseal on the sealing surfaces and to eliminate the natural tendency of asbestos to adhere to the respective opposite metallic surfaces of the cylinder head and the engine block.
The manufacture of such known cylinder head gaskets is not only relatively expensive, but it leads in some situations to objectionable results. Most known impregnating means have undesirable features relating to the durability of the soft material. Therefore, with respect to any durable gas seal below the rim borders surrounding the combustion chamber openings, complicated measures are resorted to in order to prevent as much as possible penetration of the impregnating means below the border rims. The surface coating which serves to microseal the gasket surfaces not only requires an additional manufacturing step, it also results in groove-like traces of wear on the metallic rim borders. Since, during operation of an engine, the cylinder head and the engine block execute relative movement with respect to one another in the sealing plane, the surface having grooves extending onto the rim borders parallel to the sealing plane results in the gas seal being impaired along the combustion chamber openings.
Recent developments in vehicle engines have resulted in bi-metallic and all-aluminum blocks and heads. Such engines tend to require head gaskets having increased heat conductivity and, due to higher torques utilized on the head bolts, increased crushed resistance and increased resistance to loss of torque on the head bolts.